The present invention relates generally to the field of fluid driven power hand tools, and, more particularly, to a pneumatic hammer having a new air valve therein which permits economy of manufacture and prolonged useful life of the valve.
Pneumatic ("air") hammers are power hand tools which have been commonly used in the automotive assembly and repair fields, for example for muffler and shock absorber installation or replacement. Use of such tools is also well known in various industries where disassembly of nailed or bonded components is required, such as to break up wooden loading pallets or brake shoes, for example.
The type of pneumatic hammer which is especially relevant with regard to the present invention is usually a pistol-grip style hand tool that is equipped with a free-floating steel piston housed in the rear of a steel barrel. High pressure air is forced through the air valve of the hammer and causes the piston to travel outwardly from the rear end of the barrel to the open front end thereof, thus constituting one blow of the hammer. A chisel-like tool which has been inserted into the open end of the barrel is impacted by the piston and forced outwardly therefrom to impact an object with its face which is appropriately shaped for cutting, breaking, chipping, slitting, etc., in accordance with the work to be accomplished. Typically, such impact devices impact an object in the range of about 1,000 to about 3,000 blows per minute.
A problem with some known air hammers is in the placement of the air valve at the rear end of the barrel, opposite the tool. When the piston imparts strikes to an object via the tool, the air valve may also be subject to impact as the piston returns to pre-striking position. The result of such contact between the rear end of the piston and the valve is a broken valve and an inoperable tool. In normal use the air valve in the hammer is designed to direct the incoming air behind the piston and prevent valve/piston contact. However, due to misapplication and/or barrel loosening, the valve does not always function as intended, resulting in the aforementioned broken valve.
One known style of bi-directional valve 101 in pneumatic hammers, such as that shown in FIG. 15, generally designated 100, is an assembly of the following components: two identical valve body halves 102a, 102b, a thin paper gasket 103, a valve sleeve 104, and a valve disc 106. This known valve disc 106 is a stainless steel wafer, approximately 0.035 in. thick, which shuttles between the valve halves, alternately directing high pressure air to the back and front of the piston at a rate of approximately 2100 oscillations per minute. The valve sleeve 104 is used to align the valve body halves and provide a smooth bore for consistent disc operation. Without the valve sleeve the disc is able to catch on the edges at the intersection of the mating (facing) surfaces of the valve halves during operation of the hammer.
A further problem that occurs with the old style valve design is that the constant disc shuttling during tool operation causes valve fracture. The hardness of the stainless steel disc in the known pneumatic hammer is greater than that of the usual zinc alloy valve halves. Thus, during operation the metal disc of the known valve will peen and induce stress-fracture areas in the valve body, ultimately leading to complete valve and hammer failure. Of course a great deal of time and expense is involved in dismantling a hammer and replacing the valve therein.
Accordingly, attention has been given in the present invention to overcoming these shortfalls in air valves in known pneumatic hammers. In order to protect the new bi-directional air valve from piston impacts, a resilient bumper/seal combination has been installed in the valve end of the pneumatic hammer barrel. Being in the shape of a washer, and manufactured from a polyurethane or similar resilient, elastomeric material, the bumper/seal will serve three purposes: 1) prevention of piston to valve impact by absorption of the kinetic energy of the piston; 2) provision of a positive seal between the valve and barrel to ensure the formation of an air cushion when the piston is on the return stroke; and 3) acting as an energy storage medium that will absorb piston energy upon impact and release the energy back to the piston on the forward stroke, i.e., providing a spring effect. Incorporation of the new bumper/seal into the new valve of the present pneumatic hammer results in a significant increase in value and tool durability.
Also, to reduce the stresses incurred by the valve disc a new disc design has been provided. The new disc is fabricated from a phenolic or plastic material, rather than steel, and is formed to a thickness of approximately 0.067 in. Changing to a thicker disc has resulted in the elimination of the valve sleeve. The thicker disc is sized to protrude past the seam or intersection of the facing surfaces of the new valve body halves and eliminates the possibility of catching and hanging up on the seam. Testing has shown that the new valve disc reduces the peening forces and subsequent stress build-up which occurred in the known air valve. Accordingly, the new bi-directional valve has one less component (the known valve sleeve) and also has increased durability.
The design of the two facing halves of the new air valve has also been improved to optimize valve strength and to facilitate manufacturing. The mating portions of known pneumatic air valves were designed with two tunnel-like passageways 105 (FIG. 15) that ran transversely between the valve perimeter and a trough around the valve center port. Tooling to produce tunnels 105 was complex and expensive. Sharp corners and thin wall sections were inherent in the known design, and of course valve 101 was prone to fracturing around such thin wall sections and sharp corners during hammer 100 operation.
The valve of the new fluid driven hammer as described and shown herein is manufactured with valve halves which were heretofore unknown. The improved features of the new valve include at least two curved troughs having preferably "U"-shaped cross-sections on the mating faces of the valve halves, instead of the two passageways which tunnel through the side walls of the valve. The new valve also lacks sharp corners and thin wall sections that are subject to breakage. Furthermore, the costs of parts and tooling have been reduced with the new valve design. Accordingly, the valve strength and durability have been greatly increased without changing the size of the tool or its housing, so that it is adaptable to pre-existing air hammers, and the manufacturing costs overall have thus been decreased.
As may be seen from the above, it is an object of the present invention to provide an air valve for use in a pneumatic hammer, which valve is facile and inexpensive to manufacture and which has such increased durability relative to known air valves as to substantially prolong the useful life of the valve and thus decrease repair and maintenance costs of the associated pneumatic hammer.
It is further among the objects of the present invention, having the features indicated, that the new valve be suitably constructed for use in at least some presently known pneumatic hammers, so as to provide an improved replacement for the valve originally provided therein and to not require the expense of replacement of an existing air hammer with an entirely new hammer, rather than just the air valve portion thereof.
It is also among the several objects of the invention that the new pneumatic hammer air valve have fewer parts and that it functions in a manner which is superior to valves previously known in pneumatic hammers.
Accordingly, in furtherance of the above objects the present invention is, briefly, a hammer of the type having an impact tool driven by pressurized fluid with a hammer body portion with a closed rearward end and an open forward end and a piston longitudinally movably housed within the hammer body portion for striking a tool mounted at the open forward end of the hammer body portion, to thereby impact an object with the tool. The hammer has a fluid valve housed within the closed rearward end of the hammer body portion rearwardly of the piston and in communication with a source of high pressure fluid for driving the piston. The fluid valve has a valve body portion defining an interior chamber and a continuous exterior side wall, and a longitudinal opening in communication with the interior chamber. The valve body has a first body portion and second body portion which is identical to the first body portion and positioned longitudinally in relation thereto within the closed rearward end of the hammer body portion. The first valve body portion and the second valve body portion each have a face surface and a back surface, each face surface having an identical formed well area therein. The identical formed well areas are disposed facing and coaxial to one another, thereby defining the valve interior chamber when the valve is in normal operating position. The first valve body portion and the second valve body portion each have at least one open-sided transverse channel extending from the continuous, external side wall of the wall to the internal valve chamber to thereby simplify and facilitate manufacture of the valve body, and the longitudinal opening and the open-sided transverse channels permit access of pressurized fluid through the valve chamber between the closed rearward end of the hammer body portion and the piston to direct the flow of pressurized fluid entering the valve.
The invention is also, briefly, a valve for use in a pneumatically driven hammer having a piston. The valve includes a first valve body portion and a second valve body portion. The first valve body portion and the second valve body portion each have a longitudinal opening for passage therethrough of high pressure air, a disc having a first flat side and a second flat side and which is longitudinally movably sandwiched between the first valve body portion and the second valve body portion. The disc is sized so as to be capable of rapid movement back and forth between the first valve body portion and the second valve body portion to thereby alternately direct high pressure air coming through the valve to drive the piston forwardly to strike a hammer cutting tool and to drive the piston rearwardly to a pre-striking position. The first valve body portion and the second valve body portion each have a face surface and a back surface, each face surface having an identical well formed therein, which identical wells are disposed facing and coaxial to one another, thereby defining a valve interior chamber in which the disc is movably sandwiched when the valve is in normal operating position. The first valve body portion and the second valve body portion each have at least one transverse channel in communication with the valve chamber to permit access of pressurized fluid first to one and then the other of the first and second flat sides of the disc as it moves longitudinally within the valve chamber, to thereby direct the flow of pressurized fluid entering the valve to drive the piston forward and back in the hammer body portion to strike and then return to pre-striking position repeatedly in rapid succession. The at least one transverse channel of each of the first valve body portion and the second valve body portion are open-sided, to thereby simplify and facilitate manufacture of the valve body.
The invention is also, briefly, a valve for use in a pneumatically driven hammer having a piston, which valve includes a first valve body portion and a second valve body portion. The first valve body portion and the second valve body portion each have a longitudinal opening for passage therethrough of high pressure air and each have at least one transverse channel in communication with the longitudinal opening. The valve also has a disc having a first flat side and a second flat side longitudinally movably sandwiched between the first valve body portion and the second valve body portion. The disc is sized so as to be capable of rapid movement back and forth between the first valve body portion and the second valve body portion to thereby alternately direct high pressure air coming through the valve to drive the piston forwardly to strike a hammer cutting tool and to drive the piston rearwardly to a pre-striking position. The first valve body portion and the second valve body portion each have a face surface and a back surface, each face surface having an identical well formed therein, and the identical wells are disposed facing and coaxial to one another, thereby defining a valve interior chamber in which the disc is movably sandwiched when the valve is in normal operating position. The valve disc has a thickness between the first flat side and the second flat side which permits the disc to extend beyond a seam which is formed between the adjacent face surfaces of the first valve body portion and the second valve body portion, to thereby permit the disc to oscillate longitudinally within the valve chamber without catching on a seam formed between the facing surfaces of the first valve body portion and the second valve body portion while also permitting pressurized fluid to enter the valve chamber by flowing through the at least one transverse channel of the first valve body portion and the at least one transverse channel of the second valve body portion.
These and other objects will be in part apparent and in part pointed out hereinbelow.